DE2319551B2 - CATALYST FOR OXYDATING HARMFUL EXHAUST GASES AND ITS USE - Google Patents

Description

Invention for Use «Any Specification The aluminum oxyhalide sol can be prepared

Using a catalyst of the type specified above, by placing in an aqueous aluminum oxide Aluminum, chromium and copper oxide as essential halide solution, the concentration of halides Contains constituents are found in the pre-anions reduced, so that hydrolysis and sol formation did not mention the publication. 5 entry. As time progresses, the SoI-

The invention is based on the object of a formation process for aluminum oxyhalide glycols " To create a catalyst of the type indicated, ren colloidal dimensions in the aqueous the good catalytic ^ efficiency, especially the medium are suspended. Reducing the conf The oxidation of harmful exhaust gases, with a good concentration of halide anions, can in itself mechanical catalyst stability, in particular methods known from the past. For example, can Visibly little shrinkage at high temperature, an aqueous aluminum chloride solution from an Elektrovereint and still easy and cheap to manufacture. lysis in a cell with a porous partition

The invention relates to a catalyst between the anode and the cathode, in particular for oxidizing harmful exhaust gases, whereby an aluminum, chromium and copper oxide containing an excess of chloride is obtained as essential sol from the cathode compartment. A particularly favorable method is the addition of metalsatorteilcben from a corresponding metal compound aluminum as a neutralizing agent to an aqueous aluminum chloride solution containing fertilizer in colloidal distribution. In this case, the salt formed in the course of dispersion, washing, drying and calcium neutralization is itself a hydrolycinating of the catalyst particles, ao-sizable aluminum halide, which is further characterized by the fact that it is subject to formation. A preferred method of mixing an aluminum oxyhalide sol and making the aluminum oxyhalide sol consists of a chromium oxyhalide sol in such amounts that the mixing of aluminum pellets with the corresponding amount of deionized water and calcined chromium oxide-aluminum oxide mixed poly- as addition generated from the resulting sol mixture a sufficient amount of concentrated salt contains 2 to 20 percent by weight of chromium oxide, acid to set the desired aluminum chloride gelation of the resulting sol mixture according to the container, and heating the mixture to a fixed, spherical gel reflux temperature using the known oil drop method. This leads to the desired particles, washing, drying and calcining of the gel reaction at a favorable reaction rate,
particles at a temperature of 427 to 76O ⁰ C, 30 The chromium oxyhalide sol is conveniently prepared in impregnation of the calcined particles with a similar manner as the compound providing copper oxide has been specified in such an amount of the aluminum oxyhalide sol that the final catalyst 4 to 20 and is, ie by treating an aqueous chromium (III) -preferably 4 to 12 percent by weight copper oxide halide solution to reduce its halide content, as well as drying and calcining the impregnation 35 anion concentration so that hydrolysis and sol-gnated particles in an oxidizing atmosphere occurs formation . For the reduction of the halide at a temperature of 427 to 648 ⁰ C or higher ion concentration, however, one has been made here somewhat. softening method is most expedient. So is here

The catalyst of the present invention exhibits, as shown, a reduced halide ion concentration heretofore later example with the use of the catalyst for 40, preferably by dissolving chromium trioxide in the oxidation of the exhaust gases of a motor vehicle - less than the stoichiometric amount of halogen engine It can be seen that it has good catalytic performance - hydrofluoric acid, which converts the trioxide speed and only very low shrinkage at high temperatures in the chromium (III) halide is required on. The catalyst can be carried out. The presence of trivalent chromium To ensure easy-to-prepare starting materials with a single 45 factor, the solution is reduced by a factor of 45 Procedural measures using the tion medium, z. B. formaldehyde treated. Preferably known The chromium trioxide is easily carried out and advantageously in 0.2 to 2 mol salt oil dropping method and one also simply dissolved by acid per mole of trioxide. When applying this subsequent impregnation treatment produced procedure is the indicated molar ratio for the will. 50 subsequent formation of a usable sol is essential

Other considerations and borrowings are given below. Otherwise, when reducing the preferred embodiments explained in more detail. Chromium in the trivalent state is an insoluble one

The catalyst component initially generated is a precipitate, which consists of a calcined chromium oxide-aluminum mixture with the aluminum oxyhalide sol oxide copolymer or condensate (hereinafter 55 is completely unsuitable. In contrast, Chromais is called copolymer). It is a trioxide with a hydrohalic acid in the gelation product of a sol mixture, the alumi- turn in the specified molar ratios in the niumoxyhalide and chromium oxyhalide polymer reduction contains a chromium oxyhalide sol which, for the colloidal dimensions, contains the mixing in suspension and joint gelation with that in aqueous Medium, in contrast to aluminum oxyhalide sol is well suited.
addition to, for example, previously formed aluminum The aluminum and chromium oxyhalide sols are

miniumoxide and chromium oxide with physical den in such a ratio that that from the Milling into particles of colloidal dimensions and the resulting sol mixture produced and calcined chromium dispersion in an aqueous medium to form oxide-aluminum oxide copolymer 2 to 20 Geeines Sols. The sol mixture is produced by containing 65 percent by weight of chromium oxide, separated with one another Preparation of aluminum oxyhalide and mixes. To be spherical in processing Chromoxyhalide sols and subsequent chromium oxide-aluminum oxide mixed gel particles mix in the desired ratio. the oil drop method causes premature gelation of the

S. * 6

to keep. The metal-halide ratio can be adjusted in the case of sol mixture and / or the formation of too soft spheres The final catalyst contains 4 to 20 and can be increased gradually, e.g. B. with hydrochloric acid. The spherical impregnated onto the calcined chromium oxide-aluminum-chromium oxide-aluminum oxide mixed gel particles, preferably 4 to 12 percent by weight copper oxide, produced by the oil drop method, tend to contain nium oxide particles. Conventional aging shrinkage and impregnation methods in which the calcined particles are dried when the metal to halide ratio in a solution of a copper oxide-yielding compound sol mixture is increased can be used. Changes to the metal iodide are applied. Ge-halide ratio accordingly represent a suitable copper oxide-yielding compounds are z. B. Convenient measure to control the density of the process-decomposable copper salts, such as copper (II) chloride, Kupdukts. The sol mixture is expediently in a fer (II) nitrate and copper (II) sulfate. The diluted state is preferably prepared so that it has a metal content of 8 to 20 percent by weight with a rotary dryer with a steam jacket. Sol- 15 works. The calcined chromium oxide-aluminum mixtures with a metal content of more than 20 percent by weight in the impregnation solution are slightly unstable and tend to be brought to a gel, in particular dryer, in the not yet circulating direct solidification, and for a short time left in it when mixing with the ammonia release z. B. half an hour, and then by rotation decomposable compound, or to form brittle 20 of the dryer circulated in the solution, with the and easily breaking balls. On the other hand, impregnating solutions tend to form soft gel balls, which are evaporated to dryness due to the supply of steam brine with a metal content of less than 8 wt. The impregnated material will then usually be unsuitable for further processing. mally at a temperature of 93-121 ⁰ C.

The ammonia-producing compound, which is dried with 25 and then mixed in an oxidizing Atmodem sol mixture, is a sphere at a temperature of 427 to 648 ⁰ C or a weakly basic substance, which is higher for a period of 1 Essentially stable for up to 8 hours, but calcined over time, whereby copper oxide impregnated into ammonia oxide particles can be set at the chromium oxide-aluminum and temperature. Preferably hexamethylenetetramine will be 30.

used, suitably in an amount that 1 to The catalyst may additionally comprise one or more of 2 equivalents of ammonia per equivalent of halide containing Metdloxyde arising to promote Aktiionen with complete decomposition. The amvity, selectivity and / or stability of copper oxide monia-supplying compound can thus be mixed at lower temperatures in the treatment of hot exhaust gases from processing temperatures, for example below 32 ° C, with which Sol internal combustion engines are effective, in particular mixed, without it brings about gelation in iron, nickel, cobalt, manganese, tin and / or to an appreciable extent. With the vanadium oxide. Such promoters are introduced by dispersing the sol mixture in the form of droplets. Impregnating the calcined chromium oxide-aluminum in a hot oil bath, preferably in the case of a titanium oxide particle
temperature of 48 to 105 ° C, the decomposition of the 40 The catalyst according to the invention has excellent compound initiated, and there is a sufficient Nete shrinkage resistance at high temperature gelation to form stable spherical particles. temperature up. For example, a catalyst that had only a portion of the ammonia-yielding compound put under ammonia by impregnation of a spherical aluminum is decomposed during the relatively short period of time, oxide carrier with copper oxide and chromium oxide in which the initial gelation occurs, under Am-45, a volume reduction of the release of monia. During the following 41.3% after 16 hours at 982 ° C. On the other hand, if aging continues, the decomposition of the remaining copper oxide and chromium oxide with the aluminum content of the compound occurs, and a further niuir.otyd occurs according to the rules of the invention combined neutralization and reduction of the acid anions, the shrinkage was below that the same content of the spherical particles under a further 50 conditions only 4%. The reasons for this are so far not known to the polymerization of aluminum and chromium oxy.

halide polymers and improvement of the pore For use to oxidize harmful waste

volume-pore diameter ratio. The catalyst is expediently in the form of a gas

The aging of the spherical particles is prevented by a fixed bed in a catalytic converter.

preferably in the oil at a temperature of 48 to 55 which is in the exhaust or exhaust pipe

26O ⁰ C and sufficient pressure to build it. The converter is preferably used in the

Water in the particles largely in the liquid phase Exhaust pipe so close to the engine exhaust manifold

to keep carried out. A complete hydrolysis built a mean converter inlet temperature

of the hexamethylenetetramine takes place at a temperature of at least 485 ° C and preferably above

range from 115 to 26O ⁰ C, preferably the 60 54O ⁰ C should result. Combustion air is in the hot

Do not exceed the temperature of 177 ^{° C.} In doing so, exhaust gases are placed upstream of the converter inlet

expediently introduced at a pressure of 2.6 to 10.5 atmospheres, usually by means of a suction device

worked. The duration of the aging treatment or a compressor, and the air is in the

usually carries 1 to 5 hours. Mixture with the exhaust gases through the catalytic converter

After the aging treatment, the balls 65 are conducted. The catalytic converter can be used for straight

washed with water, at a temperature of 93 flow, cross-flow or radial flow of the gas stream

Dried to 316 ° C and formed at a temperature of and can use the usual silencer

Calcined from 427 to 760 ^° C. for 2 to 12 hours. either replace or be combined with it.

example

A chromium oxide-aluminum oxide copolymer was prepared by mixing a chromium oxychloride sol with an aluminum oxychloride sol, mixing hexamethylenetetramine into the sol mixture and introducing the mixture in the form of droplets into a hot oil bath to form spherical ones Particles by the oil drop method. The chromium oxychloride sol was prepared by dissolving 200 g Chromium trioxide in 300 ml of water and addition of 68 ml of concentrated hydrochloric acid, followed by 75 ml a 37% aqueous formaldehyde solution. The addition of hydrochloric acid and formaldehyde was repeated, up to a total addition of 136 ml of concentrated hydrochloric acid and 150 ml of the aqueous formaldehyde solution. The solution was then heated at 75 ° C with evaporation of water until the weight was on 608 g had decreased, and the chromium content of this sol was reduced to 28% by dilution with water set.

The aluminum oxychloride sol used had a specific gravity of 1.3795, an aluminum-chloride ratio of 1.42 and it contained 13.96% aluminum and 9.83% chloride. The aluminum oxychloride sol was made by digesting aluminum in concentrated hydrochloric acid, like the above has been described.

The mixed sol was mixed with an equal volume of a 28% aqueous solution of hexamethylenetetramine, and the mixture was allowed to flow out as droplets into a molding tower containing hot oil; the latter was kept at 90.5 ° C. The resulting spherical particles were aged in the hot oil for 70 minutes at a pressure of 6.8 at and then washed, dried and calcined at 648 ° C. for 3 hours. The calcined chromium oxide-aluminum oxide copolymer contained 20 percent by weight of chromium oxide and 80 percent by weight of aluminum oxide. The spheres had an average bulk density of 0.342 g / cm ³ and a surface area of 139 m ² / g.

The calcined spheres were then impregnated with 4 percent by weight of copper oxide or with 10 percent by weight of copper oxide; the catalysts obtained are referred to below as catalyst A and catalyst B, respectively. Impregnation was carried out by placing the balls in an aqueous copper (II) nitrate solution and evaporating the solution to dryness using a rotary dryer with a steam jacket. The impregnated spheres were then calcined for 2 hours at 26O ⁰ C and then dried for 2 hours at ^c F.48 C.

4.5 liters of the catalyst were introduced into an exhaust converter, the in the exhaust line of a 5740-cm ³ -motor, built in 1972, was located, and the engine was a mixture of catalytically reformed gasoline and alkylate gasoline, which had an octane number of 100 , operated. The catalysts were tested by a conventional standard method (Federal Register Second Test Method 1370, Vol. 35, No. 219, November 10, 1970). In accordance with this test method, the exiting exhaust gases were diluted with air and a portion was continuously withdrawn throughout the test run. The pooled sample collected in a bag was analyzed for hydrocarbons and carbon monoxide. The catalytic converter was examined in connection with a cold-started engine and in connection with a warm-started engine; the warm start took place after the engine had been switched off for ten minutes. Furthermore, the catalyst was tested when fresh and again after twelve hours of continuous use, during which the engine was automatically controlled to operate in 4-minute cycles, each with idling, acceleration, driving and braking. The test results for the two catalysts are shown below.

Emission, g / 1.6 km mileage CO Warm start CO Cold start Hydrocarbon Hydrocarbon fabrics fabrics 3.88 1.28 Catalyst A 6.48 0.11 1.00 fresh condition 0.77 0.18 after 12 hours 0.55 2.0 0.58 Catalyst B 4.69 0.09 1.32 fresh condition 0.47 0.18 after 12 hours 0.56

It can be seen that good exhaust gas conversion and detoxification is achieved.

509584A

Claims (3)

Jy oxidation of combustible pollution components claims: th have been proposed, is the installation of a catalytic converter in the exhaust system of 1. Oxidation catalytic converter, the most suitable for aluminum, internal combustion engines. Chromium and copper oxide as essential constituents. This requires catalysts that are good contains parts and with the formation of solid catalyst activity in connection with high mechanical particles made of a corresponding metal compound. Catalyst stability, such as low shrinkage gene in colloidal distribution containing water-high temperatures have. rigen dispersion and washing, drying and It is known (US-PS 32 30 034), Oxydkataly- Calciniersn of the catalyst particles produced io sators of the type specified, which is in particular, characterized in that they are also suitable for the treatment of the exhaust gases from Verdaß by mixing an aluminum oxy-combustion engine, in the form of halide sol and a chromium oxyhalide sol aggregates of crystallites one for the Oxidation in such amounts that the chromium oxide - 15 more than 1500 Angstrom units and crystallites-like aluminum oxide copolymers - 2 to 20 equivalents in size of a weight percent melting ^{above 1000 0 C, is calcined and produced from the obtained exhaust gas active material with a size not a sol mixture:} Chromium oxide contains to create gelling of the terials. As a catalytically active component obtained sol mixture according to the known oil can, from a very large number of the specified drop method to solid spherical gel particles, substances, including copper oxide or washing, drying and calcining the gel ao copper chromite can be used as high-melting particles in a Temperature from 427 to 760 ⁰ C, zende component can, in turn, from a very impregnation of the calcined particles with a large number of substances listed there, among copper oxide supplying compound in such other also aluminum oxide or aluminum amount that the final catalyst 4 to 20 chromite can be used. The crystallites of the high and preferably 4 to 12 percent by weight copper-melting component are intended to contain the crystallites of the feroxyd, as well as drying and calcining of the catalytically active component to keep the impregnated particles apart in an oxidizing and their further growth. The atmosphere at a temperature of 427 to position takes place in most cases by mixing 648 ⁰ C or higher has been produced. precipitation from a all components or their 2. Catalyst according to claim 1, characterized in that they contain preliminary products in colloidal distribution indicates that it also has iron, nickel, aqueous dispersion. For example, a kol-cobalt, Manganese, tin and / or vanadium oxide (e) loidal dispersion or a suspension of the active as a promoter, introduced by impregnating the catalytic material in a liquid medium, Particles after the first calcination. preferably water, prepares and for this purpose the high- 3. Use of the catalyst are added after the melting component, with Spruch 1 or 2 for the detoxification of exhaust gases, the latter also in colloidal dispersion or in particular of motor vehicle engines, by suspension or on the spot by catalytic oxidation of harmful chemical conversion contained therein between suitable reactants, participants can be formed. The aggregates off 40 the crystallites of the two components are then ^{heated to 200 to 500 0} C until in this temperature unstable substances have been decomposed. Thereafter, crystallites from another material melting ^{above 1000 ° C. are expediently introduced, e.g.} B. by kneading. This further high-melting point material also serves to prevent a The invention relates to a catalyst, in particular stable growth of the catalytically active component others are to oxidize harmful exhaust gases, the aluminum to those which occur when the catalytic converter is used nium, chromium and copper oxides are essential to suppress high temperatures. More detailed parts of the figures contains and with the formation of solid catalyst- 50 moderate information about the performance of the particles from a corresponding metal compound there catalysts or in particular from Aluin aqueous containing colloidal dispersion containing diminium, chromium and copper oxide «Persion as well as washing, drying and calcining catalysts in the oxidation of harmful exhaust gases the catalyst particles has been produced. are not found, the same applies to the shrinkage Exhaust gases produced by the combustion of power or 55 behave at high temperatures.
Hydrocarbon based fuels, e.g. B. Ben- It is also known (e.g. US-PS 26 20 314), spherical iinen and fuel or heating oils, incurred, contain shaped catalyst particles, in particular made of aluminum carbon monoxide and hydrocarbons as products nium oxide, through formation of the metal oxide sol, unite incomplete combustion and throwing the sol mixed in with a compound, such as Eesa Problems relating to health and um- 60 methylenetetramine, which at elevated temperature long-term protection due to air pollution. If it is decomposed with the release of ammonia, same also exhaust gases from others with hydrocarbon dispersing the mixture in the form of droplets in fuel-operated facilities, e.g. B. a hot oil bath to gel to form solid stationary motors or machines or industrial spherical gel particles as well as washing, drying ovens, which contribute significantly to air pollution, 65 and calcining the gel particles. These the exhaust gases from automobile engines will work below, as on the main specialist source the air pollution. Commonly used in the area, summarized as an oil drop method various methods that are referred to for bringing about a. It also comes in the process of